I want to make the most fuel efficient rotary I can, I have a 13b im thinking of smaller injectors, smaller intake diamater and tuned with a safc that I have and Im not using.this is going into a b1800 truck I want it to be rotary and I want at least 25 mpg


What do you guys think, think it will work?

 

stock 13b engines even the renesis are capable of near 30 mpg if they are running right and are at a steady speed. you don't need to change anything. I've gotten nearly 27 mpg on long roadtrips in my rx8 it is possible. I've seen FC's get 30+.

if you tune it lean keep the rpms low and try to maintain a steady speed you can easily get mid to high 20's.

 

then if make the changes im telling you I might see even better results?

I just never tried to get better milage, allways more power

 

lean the engine retard the timing and it'll get much better mileage. if you have a canzoomer/blue emanage, you can do better. if you want even better mileage you can get a lower ratio rear diff gear. like a 4.1 or a 3.9 then every gear will be taller. that would really help your highway mileage.

look here

https://www.rx8club.com/mazmart-88/improved-fuel-mileage-4-1-here-78759/

 

Im using the oem one on the truck its a 3.60 I belive

 

Aseras, is there any way to make a powerful and still fuel-effecient rotary? Something like the BMW inline-6's which are powerful and very very good on fuel consumption.

 

Convert it to run on propane

 

Put the Renesis in a 1000lb car. The motor's already the most efficient rotary ever, it's just stuck in a 3000lb car.

 

^ with a 12.1 afr and a 4.44 rear diff ^

 

tuning.. rogonza, the puerto rican with the turbo 20b in a rx8 gets about the same mileage as a stock rx8 engine and has 450+ hp to the wheels.

but even if you got 60 mpg forever it'd still never pay for the 15-20K it'd cost to mod your car to that.

 

Haha, yeah I'd love to see the Renesis put on an Ariel Atom.

 

my 20b cosmo gets consistan 15 to 19 mpg city driving

now Im considering going turbo or NA, I really dont want a lot of power but 180 rwhp would be nice, it is more importand to me to get good gas milage and the truck weights 2400 pounds.

 

n/a FB's and FC's get decent mile to the gallon for a rotary... i dont think a rotary would work in a modern compact truck due to the lack of torque... unless its the 20B.

 

not really, the truck that I have a b2000 weigths just 2400 lbs, the stock motor made a wooping 86 hp and 120lbs/ft of torque and thats to the flywheel allmost any rotary engine NA or FI can beat that

 

Those values are extranious to the efficiency of the engine. That's tuning and drivetrain. Neither of which would be going into the truck.

 

I was refering to the ineficiency of the renesis tune, in fact in some areas the afr goes below the 11.0 mark

im sure a renesis in this truck would give really good milage, but my buged for this proyect its really limited, im going to work with parts that I allready have, I was looking for a truck to work and I got a b2000 for free with no engine and needing some repairs so it is a low bugget proyect but its going to rock when Im finish with it

 

3 rotor (12A based) would be really cool, but there's that budget thing again.

 

First off if you want to get gas mileage, don't follow the suggestion of a 4.44 rear end. It's already a dumb choice in the RX-8. A very important part of fuel economy isn't only air fuel ratio but rather air fuel ratio over time. An engine at a higher rpm with a leaner mixture may get worse mileage than a richer mixture run at a lower rpm. Stick to the 3.80 rear end or so but don't go over 4.10. You still need to have it tuned perfectly though.

Of course mileage is worthless if you can't get moving and it takes power to do this. Smaller fuel injectors will help slightly as they have a finer mist pattern to them. They still need to provide the same amount of fuel though. When the rotor moves around the chamber, any swirl or mixing tecniques in the engine are pretty much gone by the time it gets to the combustion point. You may or may not see any meaureable benefit from smaller injectors although the idea can't hurt as long as fuel supply is adequate.

With a taller rear end in the truck, you don't need the rpm's. You do need more low end power though so longer intake runners will be necessary. Since you intend to use a 13B, get a 6 port and keep the auxiliary ports working. Don't do what so may RX-7 owners do by losing usable power all in the name of engine bay simplicity by disconnecting them to default open.

Use a long primay exhaust system. Keep the header pipes completely separate all the way to the back of the vehicle. Then collect them at a 2.5" collector right before the muffler.

Other things you can do are to insulate anything possible. Keep as much heat as you can out of the intake manifold. Go to great lengths if necessary. Ceramic coat it, heat wrap it, whatever. Do this to the entire intake system. Get "cold air" from the front of the vehicle. Do not under any circumstances put your filter and air intake pickup point in the engine bay heat. Bad idea. Terrible for power and efficiency.

These combined with less than agressive driving habits will get you what you want. If you want to push it further in both economy and power and have a larger budget to work with, we'll talk about a small turbocharged 1 rotor. I'll leave that for another time.

 

thanks RG really helpful info there, im keepeng the stock rear, do you think I should go turbo or NA?

 

Hey guys,
I just bought up a rx8..... Been few months now did servicing and spark plug change on it..... But I don't know why the engine cuts off when I use A/C and it's kinda been a little bit fussy when I try to start it up.... I am from Fiji so any idea what's wrong?

 

Better off starting your own thread on the New Member section.

Do you have hard starting when the engine is hot, cold or both?

 

Hey bro thanks for replying......
Yes when the engine is hot it is difficult to start and when it's cold sometimes it starts easily and sometimes it takes time

 

There are lots of old threads in the Troubleshooting sections of the forum that will give you an idea of how to diagnose the cause of your hot start issue.
It could be something as simple as a weak starter (with an upgrade path to a faster spinning starter), the need for an ignition system refresh, or your engine could be suffering from low compression.

Have fun reading and researching.

BC.